Oliver Koppel says he’ll need at least half a million dollars to challenge State Senator Jeff Klein, the leader of the breakaway Democratic faction that governs the State Senate with Republicans.

Speaking on New York Post columnist Fred Dicker’s radio show this morning, Mr. Koppell, a former councilman, assemblyman and attorney general, gave himself a two week time frame to make a final call, and began to lay out “financial and organizational support” he’d need to launch the high-profile challenge.

“I want to run against Jeff Klein not because I want to be state senator–I had 23 years in Albany in the state legislature; it’s not that something I hunger for–but what Jeff Klein has done is traitorous, it’s betrayal not only of the Democratic Party, it’s betrayal of the Democratic philosophy, of the Democratic objectives,” Mr. Koppell said. “Certainly we need to spend, oh I would say, upwards of half a million dollars at least [to run a race].”

While the leader of the Tenants PAC, an influential tenants’ rights group, told Crain’s New York Business he’s ready to back Mr. Koppell if he takes the plunge, labor groups and other prominent organizations haven’t yet indicated that they’re on board.

“Unions, for instance, were reluctant to challenge Klein because they wanted him to deliver,” Mr. Koppell said. “Now he hasn’t delivered. So I hope they’re gonna come over and give us support.

Despite this weekend’s budget deal delivering on certain liberal goals like funding for universal prekindergarten in the city, Mr. Koppell accused Mr. Klein of failing to do enough for progressives.

“When it started out, Senator Klein said he wouldn’t vote for a budget unless it included de Blasio’s tax on the wealthy to pay for pre-K,” he said. “Well, there’s no tax on the wealthy to pay for pre-K and there’s no guaranteed funds. Yes, there’s money in the budget, that’s for pre-K, but it’s not guaranteed fund which is what de Blasio was talking about constantly.”

Mr. Klein did not immediately respond to a request for comment, but his spokeswoman slammed Mr. Koppell in a lengthy statement yesterday, telling Crain’s that Mr. Klein had accomplished more in the latest budget deal for working families than Mr. Koppell “has in a lifetime.”

“While Ollie Koppell has been sitting in his estate in Fieldston, Senator Klein just passed a state budget that will finally make New York more affordable for millions of working families,” said the spokeswoman, Candice Giove. “Senator Klein fought for—and won—a budget that will enroll tens of thousands of New York City four-year-olds in high-quality, universal pre-k this September.